Posts Tagged ‘Magnetic resonance imaging’

What Is fMRI?

January 11, 2014

This blog post is based on the book Brainwashed: The Seductive Appeal of Mindless Neuroscience by Sally Satel and Scott O. Lillenfeld. Please bear with me as this is the first post that I’ve written based on a source viewed on my Kindle.

fMRI is the basis for most of the brain images we see. It stands for Functional Magnetic Magnetic Resonance Imaging. Here is a brief description of how it works. Functional MRI reveals oxygen consumption and regional blood flow in the brain. Blood that is carrying more oxygen has different magnetic properties than blood that has already given up its oxygen to supply neurons. The brain will first be scanned which the participant is resting in the device to establish a baseline level. Then the participant is asked to perform a particular task of interest. The difference between this baseline and the activity when this specific task is being performed is measured and called the BOLD (blood-oxygen level response). The higher the level of oxygenated to deoxygenated blood in a particular area of the brain, the higher the energy consumption in that region. The basic unit of analysis in fMRI is called the voxel, which is a combination of volume and pixel. It is a three dimensional unit.

Subtraction is performed on a voxel by voxel level. Each voxel is then assigned a color depending on the strength of the difference in activation of that individual voxel between the control and experimental conditions. The computer then generates an image highlighting the regions that become more active in one condition relative to the other. By convention, researchers use color gradations to reflect the likelihood that the subtraction was not due to chance. A bright color like yellow might mean that the there is only one chance in a thousand that the differences are due to chance, whereas a darker color like purple might mean that the chances are higher, and that the brain differences were more likely to be attributable to random fluctuations in the data. Finally, the computer filters out background noise and prepares the data to be mapped onto a three-dimensional template of the human brain.

The final brain scan that we see rarely portrays the brain activity of a single person. Instead it almost always represents the averaged results of all participants in the study. Any resemblance between brain scans and photographs is illusory. Photos capture images in real time and space. Functional imaging scans are constructed from information derived from the magnetic properties of blood flowing in the brain. Scans are simply a representation of local activation based on statistical differences in BOLD signals.

4 Ways to Fight Alzheimer’s

June 1, 2013

This post is largely based on the article by Dr. Gary Small, “Four Ways to Save Yourself From Alzheimer’s Disease1. There is also a book by Dr. Small, The Alzheimer’s Prevention Program. The prospects for either a cure or a vaccine to prevent Alzheimer’s are becoming increasingly dim (see the healthymemory blog post, “An Update on the Prospect of a Cure for Alzheimer’s). However, there is much we can do to decrease significantly, if not avoid completely, the ravages of Alzheimer’s. This post outlines 4 ways to fight Alzheimer’s.

One way is to engage in physical exercise. The Mind Health Report notes that strength training can improve cognitive function and brain health. It also cites a study that found that walking briskly for just 20 minutes a day can lower the risk for Alzheimer’s. Walking 40 minutes a day, three times a week has also been shown to be beneficial (see the healthymemory blog post, “To Improve Your Memory, Build Your Hippocampus”). Walking is not the only beneficial activity. Jogging, swimming, and other activities pump oxygen and nutrients to brain cells. Try working these activities into daily routines.

Another way is to manage stress. Stress cannot be eliminated, nor should it be. But too much stress is harmful and increases the risk of Alzheimer’s. Cortisol-induced stress has produced temporary impairment in memory and recall abilities. Fortunately, stress can be managed. According to the Mind Health Report article, “…Dr. Helen Lavretsky at UCLA showed that tai chi can improve markers of inflammation in the blood. She also reported that functional MRI scans showed that meditation actually strengthens neural networks in important brain areas controlling cognition.” There are many healthymemory blog posts on meditation. Actually, meditation is a subtopic of the more encompassing concept of mindfulness. (enter “meditation” or “mindfulness” into the search block of this blog).

` A third way is to eat appropriately. From the article in The Mind Health Report: “For optimal brain performance, combine antioxidant fruits and vegetables with healthy proteins. Researchers at Columbia University have shown that when our diets emphasize proteins from fish and nuts along with fruits and vegetables, the risk of Alzheimer’s disease decreases compared with the risk from diets emphasizing read meat and butter and fewer fruits and vegetables.” For healthymemory blog posts on the benefits of diet enter “diet” into the search block.

The fourth way, and the way emphasized in the healthy memory blog,is through cognitive exercise. Mnemonic techniques are techniques that not only improve memory performance, but also provide beneficial cognitive exercise (See the healthymemory category “mnemonic techniques”). The healthymemory blog category, “Transactive Memory” has posts on how to employ technology and our fellow human beings in building and exercises our memories. Social relationships and interactions are important to a healthy memory. The “Human Memory: Theory and Data” healthymemory blog category provides posts on human memory and behavior., and neuroscience. You will note that the category is widely construed as human memory is at the bottom of all issues involving humans. All posts go to the goal of building a “cognitive reserve” to fight Alzheimer’s and dementia. It is never too early, or too late, to build this cognitive reserve.

1Small, G.D. (2013). Four Ways to Save Yourself From Alzheimer’s Disease. The Mind Health Report, May.

Early Testing For Alzheimer’s

March 20, 2013

Alzheimer’s disease often progresses slowly. In the early stages some level of mild cognitive impairment is experienced, but life proceeds as normal. Not everyone who experiences this mild cognitive impairment will progress into Alzheimer’s. They have a twelve percent chance of developing it each year. Some will never develop dementia or will develop it from causes other than Alzheimer’s disease.1

Substantial effort has gone into developing tests to identify those with mild cognitive impairment who will progress into Alzheimer’s. This is difficult as a definite diagnosis awaits finding the amyloid plaques and neurofibril tangles. Positron emission tomography (PET) scans have been done to search for amyloid plaques in the brain that may begin to appear before symptoms manifest themselves. Research has found that healthy people with these plaques in their brains are more likely to develop Alzheimer’s related dementia later in life. However, it should be remembered that although these plaques and tangles might be a necessary condition for Alzheimer’s, they are not a sufficient condition. They have been found in autopsies of people who never exhibited any symptoms. The notion is that they had a cognitive reserve that protected them from this damage.

Tests can employ PET scans and/or Magnetic Resonance Imaging (MRI) scans along with analyses of brain fluid. I have seen no data regarding the accuracy of these tests with respect to hits (correct diagnosis) versus false alarms (incorrectly diagnosing progression into Alzheimer’s). Moreover, none of the current tests can help determine whether a person with early signs will progress quickly to dementia or continue to live normally for years.2

MRI’s have been successful in treating a condition that is frequently been misdiagnosed as Alzheimer’s (See the healthymemory blog post, “A Treatable Condition Misdiagnosed as Alzheimer’s). The condition is Normal Pressure Hydrocephalus and occurs when the cerebrospinal fluid that surrounds the brain is not re-absorped. It is estimated that 5% of the people diagnosed with dementia have this condition. Unlike Alzheimer’s, this condition can be corrected.

It is somewhat ironic that early testing for Alzheimer’s can be beneficial for the diagnoses of conditions other than Alzheimer’s. Currently Alzheimer’s cannot be cured. Drugs can slow the progression of the disease, but one should consider, is this simply prolonging the agony of the sufferer? When there are opportunities for participating in a test of a new treatment, one can volunteer in the spirit of contributing to science and the development of a possible cure, but realizing that there will likely be adverse events and the likelihood of a personal cure is quite low.

There is some evidence that people can actually reduce their risk of dementia by quitting smoking, living a heart-healthy lifestyle, and treating any diabetes or hypertension that might be present. The healthymemory blog would add being both cognitively and physically active; to continue to grow cognitively, and to build and maintain social relationships. Most healthymemory blog posts address these topics. I would hope that they all make, at least, some small contribution to cognitive growth.

1Wolfe, S.M. (ed) (2013) Early Testing for Alzheimer’s. Public Citizen Health Letter, February, Vol 29, No. 2. 4-5.

© Douglas Griffith and healthymemory.wordpress.com, 2012. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and healthymemory.wordpress.com with appropriate and specific direction to the original content.

2Ibid.

An Amazing Example of the Neuroplasticity of Memory

June 26, 2011

The Washington Post published an article1 about a woman, Su Meck, who lost her memory when she was 22. A ceiling fan fell on her head, erasing her memory. After a week in a coma she awoke with the mental capacity of a young child. She did not recognize her husband or her two baby sons. She could no longer read or write, walk, eat, dress, drive, and she could barely speak. An MRI scan revealed that her brain was suffused with cracks. It was said that it looked like shaken Jell-O. She had complete retrograde amnesia, the inability to remember the past. Initially she could not learn new information, so her hippocampi apparently had also been damaged. She had lost her personality.

Fortunately she had a very supportive family. They patiently worked with her. Her mother assembled a photo album filled with images of the childhood she had completely forgotten. She actively tried to regain her lost capacities. She relearned her muliplication tables from her children. She volunteered in her children’s school library so she could hide in the stacks and read. During the first few years talking on the telephone was disorienting, so she communicated with her family using letters. She had the spelling and penmanship of a small child.

When she left the hospital she completed a checklist of tasks that she wanted to accomplish such as riding a bicycle, preparing a meal and reading a children’s book. The first book she read was Dr. Seuss’s “Hop on Pop.” Her functionality gradually returned. When she drove home, she had difficulty remembering where home was so she would click her garage door opener looking for a hint as to which address was hers.

Nineteen years after the accident Su started Montgomery Junior College. Her children gave her tips on what to bring to class, how to take notes, how to ask questions, and how to write papers. Learning was difficult and slow. But she persevered and struggled along until she learned. And she learned well. She earned her associates degree with a 3.9 average and became chapter president of the Phi Theta Kappa honor society. Su and her husband are planning to move to Massachusetts where she will enroll in Smith college as a transfer student and start working on her bachelor’s degree.

This is the most remarkable example of neuroplasticity of which I am aware. How could she possibly do this? I think there are two essential elements. She had a very supportive family who perservered under adverse circumstances and stuck with her all the way. Su also deserves most of the credit herself. She believed in herself under the most adverse circumstances and persevered to where she was able to return to her own self and continue her life. Lesser individuals likely would remain in a vegetative state or only achieve modest degrees of recovery.

1de Vise, D. (2011) Gaithersburg Woman Earns a College Degree Two Decades After Complete Memory Loss. Washington Post, 21 May.

© Douglas Griffith and healthymemory.wordpress.com, 2011. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and healthymemory.wordpress.com with appropriate and specific direction to the original content.

Two Brains, One MRI Scanner

May 18, 2011

The New Scientist reported that Ray Lee of Princeton has developed the first dual-headed fMRI scanner.1 Up until now these machines had been unable to handle more than one brain at a time. And for reasons that I don’t understand (because I don’t understand the technology), they cannot synchronize two or more scanners to scan different individuals at the same time. Although they can scan people in different machines and link them by video. But Lee has designed his scanner that scans two brains at the same time in the same scanner.

In one of the first tests, Lee asked couples to face each other and to blink in unison. The fusiform gyrus, which is involved in facial recognition, was tightly correlated in the two brains. He also had couples embrace, which revealed similar synchronous brain activity.

James Coan of the University of Virginia has some interesting ideas on how to use this device. He notes that “People distribute neural processing across multiple brains when solving problems. …You essential contract out part of a given problem to someone else’s mind. Lee’s work would give us the opportunity to see two brains reacting to a problem simultaneously.” Using the terminology of the Healthymemory Blog, this activity involves transactive memory, memories that are stored in someone else’s brain.

Many of our activities involve, either implicitly or explicitly, transactive memory. When you are trying to communicate with somebody or some group, successful communication requires that the material be pitched at the appropriate level. This entails knowing something about what the other party(ies) knows. When you are trying to persuade somebody, it is extremely helpful to know what that person knows and believes. And it games, you are constantly trying to decipher what the other person is thinking. Transactive memory is a big player in many activities.

1Ferris jabr (2011). At last, an MRI scanner for the man with two brains. New Scientist, 29 January, 12. 

© Douglas Griffith and healthymemory.wordpress.com, 2011. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and healthymemory.wordpress.com with appropriate and specific direction to the original content.

To Improve Your Memory, Build Your Hippocampus

April 24, 2011

A previous post, “If You Do Not Like Mnemonic Techniques, Try Walking”, was a little thin given the importance of the topic. So I’ve gone to the original article1. The hippocampus is a component of the brain that is critical to memory function. Unfortunately, the hippocampus shrinks 1-2% annually in older adults without dementia, and this loss of volume increases the risk of developing cognitive impairment. This experiment was undertaken to assess whether exercise and what kind of exercise might mitigate this decline.

Participants between the ages of 55 and 80 years old were recruited, who did not have any pertinent diseases or disabilities. 120 participants were randomly assigned: half to a stretching and resistance training control group, and half to an aerobic walking group. Sessions for each group were held three times a week and lasted roughly one hour. Participants in the aerobic group started walking for ten minutes the first week and increased walking durations by five minute increments until a duration of 40 minutes was reached by week seven. Each session began and ended with approximately 5 minutes of stretching. The control group engaged in four muscle-toning exercises using dumbbells or resistance bands, two exercises designed to improve balance, one yoga sequence and one exercise of their choice. The program lasted for one year. MRIs, fitness, and short term memory were assessed before the program began, 6 months into the program, and at the end of the one-year program. Blood samples were taken at the beginning and end of the program.

Aerobic exercise (walking) increased hippocampal volume by 2%. This increase effectively reverses the expected age-related loss by 1 to 2 years. Moreover, increased hippocampal volume was positively correlated with improvements in short term memory performance. Increased hippocampal volume was also associated with greater levels of serum Brain-derived neurotrophic factor (BDNF), which helps support the survival of existing neurons and encourages the growth and differentiation of new neurons and synapses.

Hippocampal volume did decrease in the control group, but higher preintervention fitness partially attenuated the decline. The control group also exhibited improvement in short term memory performance.

Changes in fitness are associated with increased hippocampal volume. The aerobic exercise group showed a 7.78% improvement in maximal oxygen consumption (VO2) after intervention, whereas the stretching control group showed a 1/11% in VO2 max.

So although both exercise regimes were beneficial, the aerobic regime appeared to be more beneficial, especially with respect to its beneficial effects on hippocampal volume. Given the importance of the hippocampus to brain and memory, this finding is extremely important. Moreover, this aerobic exercise regimen was fairly mild and undemanding.

1Erickson, K.I., Voss, M.W., Prakash, R.S., Basak, C., Szabo, A., Chaddock, L., Kim, J.S., Heo, S., White, S.M., Wojcicki, T.R., Malley, E., Viera, V.J., Martin, S.A., Pence, B.D., Woods, J.A., McAuley, E., & Kramer, A.F. (2011). Exercise Training Increases Size of Hippocampus and Improves Memory. PNAS Early Edition, www.pnas.org/cgi/doi/10.1073/pnas.10159550108.

Does Meditation Promote a Healthy Memory?

April 20, 2011

An interesting article1 in AARP online describes the benefits of meditating. It cites a study done by Harvard University and Massachusetts General Hospital in 2005. It found that a group practicing meditation for about 40 minutes a day had measurably thicker tissue in the left prefrontal cortex. This is an area of the brain important to cognitive emotional processing and well-being.

At the UCLA Laboratory of Neuro-Imaging the brains of experienced mediators were compared with a control group of nonmediators. The mediators’s brains contained more gray matter than those of the nonmediators. This gray tissue is responsible for high-level information processing especially in the areas associated with attention, body awareness and the modulation of emotional responses.

In a study published in 2010, neuroscientists scanned the brains of volunteers before and after they received eight weeks of training in Mindfulness-Based Stress Reduction (MBSR). They found growth in the hippocampus and shrinkage in the amygdala. As readers of the Healthymemory Blog probably know, the hippocampus is an important part of the brain that is critical to memory and learning. The amygdala is a portion of the brain that initiates the body’s response to stress.

An MRI study at Emory University showed that experienced meditators were much better than a nonmeditating control group at ignoring extraneous thoughts and focusing on the matter at hand when bombarded by stimuli. This capability to focus at will is especially important in today’s multitasking world when we are constantly bombarded by information, often noise, from a variety of sources. This capability grows more important as we age, because research has indicated that the elderly have more difficulty focusing their attention that those who are younger.

Meditation along with positive emotion might even result in a healthier immune system.

This quote from Dr. Richardson is worth remembering. “We know that the brain is the one organ in our body build to change in response to experience and training. It’s a learning machine.”

It should be understood that meditating does not require going to an ashram or sitting in the lotus permission. Here are some guidelines for meditating that were provided in the AARP article.

  1. Sit in any position that’s comfortable for you; a chair is fine. Or, and this is my personal favorite, you can lie down.

  2. Start with a 5-minute session and then gradually increase to longer times.

  3. Start by just feeling your breath as it enters and leaves your nostrils. You don’t need to adjust the breath to make it deeper or finer; simply notice it as it is and as it changes.

  4. Sometimes thoughts or emotions come up and sweep us away, or we fall asleep. Know that your mind will wander, just notice where it went and then gently bring it back to the breath—every time, over and over.

  5. Above all, have patience with yourself. The more you practice meditation, the easier it gets to stay focused. So don’t get discouraged by your wandering mind. Eventually, it will get easier to return to concentrating on your breathing.

I would add that whenever you feel stressed or upset, it is a good idea, if possible, to go someplace where you will no be noticed and try to meditate. Even five minutes can be helpful in such situations.

1Salzberg, S. www.aarp.org/personal-growth/life-long-learning/info-0202011/meditation_grows_t…, February 25, 2011

© Douglas Griffith and healthymemory.wordpress.com, 2011. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and healthymemory.wordpress.com with appropriate and specific direction to the original content.

 

Walking and a Healthy Memory

February 2, 2011

The Health Day Newsletter contained an article1 summarizing a news release from the November 29, 2010 meeting of the Radiological Society of North America. The research suggests that walking about five miles a week may help slow the progression of cognitive illness among seniors already suffering from mild forms of cognitive impairment or Alzheimer’s Disease. The research also indicated that walking just six miles a week can help prevent the onset of disease.

Two appealing features leap out at me from this news. First is the cost. Walking costs nothing (unless you choose walking shoes or consider the minimal wear placed on shoes). Secondly, this is a reasonable regimen. Six miles is not excessively demanding, particularly when you consider that it can be spread out over an entire week.

3-D MRI scans were done to measure brain volume. After accounting for age, gender, body-fat composition, head size, and education, it was found that the more the individual engaged in physical activity, the larger the brain volume. Greater brain volume is a sign of a lower degree of brain cell death as well as general brain health. Cognitive tests were also administered and these also indicated improved cognitive performance in healthy individuals and lower losses in cognitive performance for those who already had begun to decline cognitively.

Physical activity improves blood flow to the brain, changes neurotransmitters, and improves cardiac function. It also lessens the risk of obesity, improves insulin resistance and lowers the risk of diabetes, and lowers blood pressure, All of these things are risk factors for Alzheimer’s disease.

Clearly the Healthymemory Blog endorses physical activity in addition to the mental activities advocated in this blog. These include mnemonic techniques and transactive memory. Transactive memory entails cognitive growth via technology and our fellow human beings.

1Regular Walking May Slow Decline of Alzheimer;s, http://consumer;healthday.com/Article.asp?AID=646656

© Douglas Griffith and healthymemory.wordpress.com, 2011. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and healthymemory.wordpress.com with appropriate and specific direction to the original content.